Systems and techniques for automatically detecting occurrence of specific event in a video image in a real-time manner, using an image recognition technique, are developed. A specific person detection system is known as typical one of such systems. The specific person detection system is a system having a function of automatically detecting a person previously image-registered as a detection object (hereinafter, specific person), when appears in a monitored video image, and notifying a system operator of the detection of the person. The detection is performed by collation of image feature value between a specific person's image and images of a person appeared in the monitored video image (appeared person), to calculate coincidence between both persons' images, and when the coincidence is a value within a certain range, determining that they are the same person, i.e., the specific person.